JP2009050104A - Dc power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC power supply circuit with a simple structure capable of appropriately achieving stepping up/down of output voltage. <P>SOLUTION: This DC power supply circuit includes: a first series circuit which is arranged between input terminals on the positive side of the DC power supply circuit and includes a self inductor, a capacitor, a first inductor and a rectifier diode; a switching element for alternately switching the self inductor between in a conduction state and in a non-conduction state; a second inductor of which one end is connected to one end of the capacitor and magnetically coupled to the first inductor, while the other end is connected to the negative side of the DC power supply circuit. When the turns ratio of the first inductor to the second inductor is 1:1, for example, the relation between a battery voltage E and an output voltage Vo can be expressed as Vo=2DE/(1-D), where D is a duty ratio. This enables stepping up/down of the output voltage Vo in a wider range than before. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a DC power supply circuit, and more particularly to a DC power supply circuit suitable for driving an illumination LED such as an automobile.

  In recent years, light emitting diodes (hereinafter referred to as LEDs) are increasingly used as light sources for display devices and lighting devices. In particular, LEDs have the characteristics of low power, high brightness, and long life, and can be said to be one of the illuminating devices of interest, as low power consumption and high quality are required in all products. For these reasons, recently, it is also used in automobile headlamps, etc., which have extremely high quality requirements.

  Conventionally, when an LED is used as a light source, it is required to stabilize a supply current to the LED in order to make the light emission amount, luminance, and the like constant. In addition, when used for a vehicle such as an automobile, the power supply is an in-vehicle battery. The voltage value of the battery is, for example, 6V to 24V, and the range of the value is large, and the number of LEDs used is also large. It depends on the vehicle type and usage.

  Therefore, conventionally, for example, a boost type power supply as shown in Patent Document 1 has been used. Here, for the sake of explanation, a similar boost type power supply will be described with reference to FIG. In FIG. 3, the positive terminal and the negative terminal (+ B, −B) of the battery are connected to the input terminal of the power supply circuit, respectively, and the inductor L10 and the diode D10 are connected in series to + B, and the cathode of the diode D10 A capacitor C10 and an LED LAMP are connected between the capacitor and GND. In addition, one end of a switching element that alternately switches the inductor between a conducting state and a non-conducting state is connected between the inductor L10 and the anode of the diode D10, and the other end is connected to GND, and is controlled by the control unit.

As described above, when used in a vehicle such as an automobile, the assumed voltage range of the battery is wide, for example, from about 6 V to 24 V, while the minimum battery voltage is specified when the output voltage is 100 V, for example. Assuming 6V, a circuit for boosting the output voltage to 100V is required. However, in the circuit of Figure 3, a battery voltage E, the output voltage Vo, the duty ratio of the switching element _{D (D = T ON / (} T OFF + T ON), T ON: ON _time, T OFF: OFF time) Then, the relationship between the battery voltage E and the output voltage Vo is Vo = E / (1-D). Here, generally, if the MAX value of the duty ratio D is 0.9, Vo = 10E. Therefore, the above-mentioned specification cannot be satisfied with the circuit of FIG. 3, ie, the conventional boost type circuit.

On the other hand, when the battery voltage is 24V and the output voltage is, for example, 15V, the MIN value of the duty ratio D is 0 from the above relational expression in the circuit of FIG. E is the smallest output voltage and cannot satisfy these requirements. For this reason, conventionally, as shown in FIG. 4, a switching device Q20 and a diode D20 are added to the circuit shown in FIG. It was going to narrow down to.
JP 2005-80353 A

  However, even if the circuit of FIG. 4 can narrow the output voltage to the input voltage or less, the configuration of the booster circuit is the same as that of FIG. There was a problem that I couldn't. There is also a problem that the circuit configuration is complicated.

  Therefore, the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a DC power supply circuit that can realize optimum boosting and stepping down of an output voltage with a simple configuration.

In order to solve the above-described problems, the present invention proposes the following matters.
(1) The present invention is a DC power supply circuit for supplying power to a load, and is arranged between the positive and negative input / output terminals of the DC power supply circuit, and is self-inducted (for example, equivalent to the inductor L1 in FIG. 1), a capacitor (for example, 1), a first series circuit including a first inductor (for example, equivalent to the inductor L3 in FIG. 1), a rectifying diode (for example, equivalent to the diode D1 in FIG. 1), A switching element (for example, equivalent to switching element Q1 in FIG. 1) that switches the self-inductor alternately between a conductive state and a non-conductive state, and one end of which is connected to one end of the capacitor and magnetically coupled to the first inductor A second inductor (for example, equivalent to the inductor L2 in FIG. 1) having the other end connected to the negative electrode side of the DC power supply circuit. It has proposed a DC power supply circuit to the butterflies.

  According to the present invention, since the first inductor and the second inductor are provided, if the winding ratio is 1: 1, for example, the relationship between the battery voltage E and the output voltage Vo is duty cycle. When the ratio is D, Vo = 2DE / (1-D). Therefore, when D = 0.9, the output voltage Vo can be boosted to 18 times the battery voltage E, and when D = 0.1, the output voltage Vo is stepped down to 0.22 times the battery voltage E. it can.

  (2) The present invention proposes a DC power supply circuit characterized in that, for the DC power supply circuit of (1), the load is composed of at least one LED.

  According to the present invention, since the load is configured by at least one LED, a flexible power source can be configured according to specifications.

  (3) The present invention proposes a DC power supply circuit characterized in that, in the DC power supply circuit of (1), a winding ratio between the second inductor and the first inductor is 1: n. ing.

  According to the present invention, since the winding ratio between the second inductor and the first inductor is 1: n, it is possible to provide further freedom for both step-up and step-down.

  (4) According to the present invention, in the DC power supply circuit of (1) to (3), a resistor (for example, corresponding to the control unit in FIG. 1) is provided on the output terminal side, and a current value flowing through the resistor becomes constant. A DC power supply circuit characterized by comprising a control unit for controlling the switching timing of the switching element is proposed.

  According to the present invention, the resistor is provided on the output terminal side, and the switching timing of the switching element is controlled so that the value of the current flowing through the resistor becomes constant. Therefore, constant current driving is performed while supplying an appropriate voltage to the load. be able to.

  (5) According to the present invention, in the DC power supply circuit of (4), short mode detection means for detecting the short mode of the load and stepping down the supply of voltage to the load (for example, corresponding to the control unit in FIG. 1) The DC power supply circuit characterized by having provided is proposed.

  According to the present invention, since the short mode of the load is detected and the supply of the current to the load is stopped, in normal times, an appropriate current is supplied while a problem occurs in the load, and the short mode is set. In some cases, by stopping the supply of current to the load, it is possible to prevent the apparatus from generating heat or discharging the battery.

  According to the present invention, since the step-up rate is much higher than before, for example, when the load is an LED, there is an effect that it is possible to supply a power source that can cause the LED to emit light with high luminance. In addition, since the output voltage, which is the voltage applied to the load, can be set lower than the input battery voltage, for example, when the load is an LED, the brightness can be adjusted as necessary. There is. Further, normally, when the load is in the short mode while supplying an appropriate voltage, the voltage to the load is stepped down, so that it is possible to prevent the device from generating heat and discharging the battery.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the constituent elements in the present embodiment can be appropriately replaced with existing constituent elements and the like, and various variations including combinations with other existing constituent elements are possible. Therefore, the description of the present embodiment does not limit the contents of the invention described in the claims.

<Circuit configuration>
FIG. 1 shows a circuit configuration of a DC power supply circuit according to an embodiment of the present invention.
In FIG. 1, a battery E is connected to the input terminal. Further, a self inductor L1, a capacitor C2, a first inductor L3, and a diode D1 are connected in series to the positive line (+ B) of the battery E.

  Further, a capacitor C1 is arranged in parallel with the battery E, one end of the switching element Q1 is connected between the self-inductor L1 and the capacitor C2, and the other end is connected to the negative electrode side. One end of the second inductor L2 is connected to one end of the capacitor C2, and is magnetically coupled to the first inductor L3, and the other end is connected to the negative electrode side.

  A capacitor C3 is connected to the cathode of the diode D1, and the other end is connected to the negative electrode side. The voltage dividing resistors R1 and R2 are connected in parallel with the capacitor C3, and the resistor R3 is connected in series with the negative electrode side line.

  The switching element Q1 is duty-controlled by the control unit, and the voltage dividing points of the resistors R1 and R2 and one end of R3 are also connected to the control unit. An LED LAMP is connected to the output terminal. In the present embodiment, the resistor R3 is provided on the negative electrode side, but may be provided on the positive electrode side.

  Here, the battery E is a vehicle-mounted battery, and its voltage value is assumed to be about 6V to 24V. The capacitor C1 is for removing high-frequency noise from the battery E. When the switching element Q1 is turned ON, the inductor L1 flows a current I1 and generates a voltage V1 as shown in FIG.

  The switching element Q1 is duty-controlled by the control unit, thereby generating a desired output voltage. The capacitor C2 is charged with the voltage V1 generated by the self-inductor L1, and when the switching element Q1 is turned off, the current I2 flows through the inductors L2 and L3 in the direction I2 in the figure, and the voltages V2 and V3 as shown in FIG. Occurs.

  Therefore, if the winding ratio between the inductor L2 and the inductor L3 is 1: 1, the relationship between the battery voltage E and the output voltage Vo is Vo = 2DE / (1 when the duty ratio is D. -D). Thus, when D = 0.9, the output voltage Vo can be boosted to 18 times the battery voltage E, and when D = 0.1, the output voltage Vo can be up to 0.22 times the battery voltage E. Can step down.

  When the winding ratio between the inductor L2 and the inductor L3 is 1: n, the relationship between the battery voltage E and the output voltage Vo is Vo = DE / (1-D) + nDE / (1- D). Therefore, the step-up value and the step-down value can be set more flexibly by changing the winding ratio between the inductor L2 and the inductor L3.

  The diode D1 and the capacitor C3 smooth the voltage supplied to the LED LAMP. The resistor R3 converts the current flowing on the negative electrode side through the LED LAMP into a voltage and supplies the voltage to the control unit. The control unit performs switching so that the voltage value supplied to the control unit becomes a predetermined value. The LED LAMP is driven with a constant current by finely controlling the duty of the element Q1.

  The resistors R1 and R2 generate a divided value of the supply voltage Vo to the LED LAMP and supply it to the control unit. In the control unit, the LED LAMP is in the short mode when the resistance R3 is higher than a predetermined value even by delicate duty control of the switching element Q1, and when the divided voltage values of the resistances R1 and R2 are lower than the steady value. Therefore, the duty of the switching element Q1 is set to 0, the supply to the LED LAMP is cut off, and the supply of current to the shorted LED LAMP is stopped.

  As described above, according to the present embodiment, since the step-up rate is much higher than the conventional one, for example, when the load is an LED, it is possible to supply a power source that can cause the LED to emit light with high luminance. Moreover, since the output voltage which is an applied voltage to the LED can be set lower than the input battery voltage, the brightness can be adjusted as necessary. Further, normally, when the load enters the short mode while supplying an appropriate voltage, the supply of current to the load is stopped, so that the heat generation of the device and the battery discharge can be prevented.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, A various deformation | transformation and application are possible within the range which does not deviate from the summary of this invention.

It is a connection diagram showing an example of a DC power supply circuit according to the present embodiment. 2 is a timing chart of main voltages and currents in the circuit shown in FIG. 1. It is a connection diagram showing an example of a boost type power supply according to a conventional example. It is a connection diagram which shows an example of the buck-boost type power supply which concerns on a prior art example.

Explanation of symbols

  E: Battery, C1, C2, C3, C10 ... Capacitor, L1, L2, L3L10 ... Inductor, Q1, Q10, Q20 ... Switching element, D1, D10, D20 ... Diode, R1 , R2, R3... Resistance

Claims (5)

In a DC circuit that supplies power to a load,
A first series circuit disposed between positive input terminals of the DC power supply circuit and including a self-inductor, a capacitor, a first inductor, and a rectifying diode;
A switching element that alternately switches the self-inductor between a conductive state and a non-conductive state;
A second inductor having one end connected to one end of the capacitor and magnetically coupled to the first inductor, and the other end connected to the negative electrode side of the DC power supply circuit;
A DC power supply circuit comprising:   2. The DC power supply circuit according to claim 1, wherein the load comprises at least one LED.   3. The DC power supply circuit according to claim 1, wherein a winding ratio between the second inductor and the first inductor is 1: n. 4.   4. The control device according to claim 1, further comprising: a control unit configured to provide a resistor on the output terminal side and control a switching timing of the switching element so that a current value flowing through the resistor becomes constant. DC power supply circuit.   5. The DC power supply circuit according to claim 4, further comprising short mode detection means for detecting a short mode of the load and stepping down the supply of voltage to the load.

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